This paper has three aims. First, I’ll argue that there’s no good reason to accept any kind of ‘easy knowledge’ objection to externalist foundationalism. It might be a little surprising that we can come to know that our perception is accurate by using our perception, but any attempt to argue this is impossible seems to rest on either false premises or fallacious reasoning. Second, there is something defective about using our perception to test whether our perception is working. What this reveals is that there are things we aim for in testing other than knowing that the device being tested is working. I’ll suggest that testing aims for sensitive knowledge that the device is working. Testing a device, such as our perceptual system, by using its own outputs may deliver knowledge, but it can’t deliver sensitive knowledge. So it’s a bad way to test the system. The big conclusion here is that sensitivity is an important epistemic virtue, although it is not necessary for knowledge. Third, I’ll argue that the idea that sensitivity is an epistemic virtue can provide a solution to a tricky puzzle about inductive evidence. This provides another reason for thinking that the conclusion of section two is correct: not all epistemic virtues are to do with knowledge